This invention relates to multiplexers of microwave electromagnetic signals and, more particularly, to a composite structure of a Butler Matrix with quantized delay units for nulling phase tapers at each of a plurality of input frequency channels and providing a distribution of each of a plurality of input signals among a plurality of output ports while retaining a uniform distribution of signal amplitudes throughout the multiplexer.
Multiplexers are widely used in signal processing operations. One example of the use of a multiplexer is in a communication system such as a direct broadcast system employing a satellite carrying an array antenna positioned for transmitting a plurality of signals at different frequencies to a designated region of the earth. It is the practice, upon receipt of the signals at the satellite, to amplify each of the signals in a separate channel, after which the signals are combined into a single transmission line coupled to the input port of a power splitter. The power splitter divides the signal power evenly among a set of radiators of the antenna to form a beam of electromagnetic power which carries the signals to earth.
However, a problem arises in the use of the foregoing single channel coupled to the input of the power splitter. The summing of all the signals in the single channel produces intense electric and magnetic fields which are prone to nonlinear effects, such as may occur under intense field strength at the interfaces between waveguide flanges which join the waveguides of a microwave circuit. A nonlinear effect introduced upon the sum of a plurality of signals results in intermodulation products which corrupt the individual signals. As a result, signals communicated by presently available satellite communication systems may have less fidelity than is desired.